The Shining is one of two films with a higher rating than the book. King famously hates the film

"Are you mystified by the cult that's grown around Kubrick's Shining?I don't get it. But there are a lot of things that I don't get. But obviously people absolutely love it, and they don't understand why I don't. The book is hot, and the movie is cold; the book ends in fire, and the movie in ice."

To make this a fair test films and book would have to be graded on a curve. By what the average rating of each is. There is a good discussion on how to normalise the original comparison here. But I think this graph is enough to show Stephen King books are better than his films.

Less than 8% of King adaptations are rated higher compared to 26% usually for book adaptations. To get King to have the average quality of adaptations, sixish Stephen King Films being rated better than is books. This would require Dolores Claiborne, The Green Mile, Stand By Me, Misery and maybe Carrie to be much worse books or these already highly rated films to be much better. I am going to call this Myth Busted*, Stephen King adaptations are less successful than the average adaptation.